The storage capacity of conventional hard disk drives has greatly increased over recent years. Advances in disk drive technology have decreased the surface area required to reliably and retrievably store a bit along a “track” on the disk surface, and have also decreased the spacing between adjacent tracks. This reduction in the active disk surface area per unit of storage has been enabled, in large part, by corresponding reductions in the size and precision of magnetic transducer elements, often referred to as “heads,” used for reading and writing operations in magnetic disk drives.
A magnetic disk drive includes, in a basic implementation, one or more rotating magnetic disks on which data can be stored, read and write heads that are suspended adjacent to a surface of the magnetic disk(s) by a suspension arm, and an actuator which controls a position of the suspension arm so as to place the read and write heads over selected tracks on the rotating magnetic disk(s) during reading and writing operations. Two key technologies in achieving higher storage density in hard disk drives are a reduction in the clearance between the read/write head and the magnetic disk and the minimization of flying height variations to maintain low bit error rates.
As the suspension arm flies over the surface of the rotating magnetic disk, the spacing between the read/write head and the magnetic disk defines the flying height. The performance of read and write operations in the disk drive increases exponentially with decreased flying height, and thus the read/write head is generally positioned as close to the surface of the disk as possible. However, the read/write head cannot physically contact the disk, since this could result in damage to the head and/or disk (e.g., hard disk crash). Consequently, the read/write head must be spaced far enough from the surface of the magnetic disk to accommodate for flying height variations which may occur during operation of the disk drive, including, for example, differences in disk thickness and/or planarity resulting from manufacturing and deformations caused by thermal expansion of the disk and/or head.